Prospective diagnostic test accuracy of transvaginal ultrasound posterior approach for uterosacral ligament and torus uterinus deep endometriosis

OBJECTIVE: To determine the diagnostic test accuracy of transvaginal ultrasound (TVS) using a standardized technique for the diagnosis of deep endometriosis (DE) of the uterosacral ligaments (USLs) and adjacent torus uterinus (TU). METHODS: This was a prospective diagnostic test accuracy study conducted at the McMaster University Medical Center Tertiary Endometriosis Clinic, Hamilton, ON, Canada. Consecutive participants were enrolled if they successfully underwent TVS and surgery by our team from 10 August 2020 to 31 October 2021. The index test was TVS using a standardized posterior approach performed and interpreted by an expert sonologist. The reference standard included direct surgical visualization on laparoscopy by the same person who performed and interpreted the ultrasound scans. Accuracy, sensitivity, specificity, positive and negative predictive values (PPV and NPV) and positive and negative likelihood ratios were calculated for the TVS posterior approach for each location using the reference standard. RESULTS: There were 54 consecutive participants included upon completion of laparoscopy and histological assessment. The prevalence of DE for the left USL, right USL and TU was 42.6%, 22.2% and 14.8%, respectively. Based on surgical visualization as the reference standard, TVS demonstrated an accuracy of 92.6% (95% CI, 82.1-97.9%), sensitivity of 82.6% (95% CI, 61.2-95.1%), specificity of 100% (95% CI, 88.8-100%), PPV of 100% and NPV of 88.6% (95% CI, 76.1-95.0%) for diagnosing DE in the left USL. For DE of the right USL, TVS demonstrated an accuracy of 94.4% (95% CI, 84.6-98.8%), sensitivity of 75.0% (95% CI, 42.8-94.5%), specificity of 100% (95% CI, 91.6-100%), PPV of 100% and NPV of 93.3% (95% CI, 84.0-97.4%). For DE of the TU, TVS demonstrated an accuracy of 100% (95% CI, 93.4-100%), sensitivity of 100% (95% CI, 63.1-100%), specificity of 100% (95% CI, 92.3-100%), PPV of 100% and NPV of 100%. CONCLUSIONS: We observed high diagnostic test accuracy of the evaluated standardized TVS technique for assessing DE of the USLs and TU. Further studies evaluating this technique should be performed, particularly with less experienced observers, before considering this technique as the standard approach. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.